The invention relates to a system for controlling a power-driven window movable in a window opening between closed and open positions.
One such system is shown, for example, in French patent specification No. 2,098,871. In this system, for controlling a power-driven window in a motor vehicle, an electrical conductor is incorporated into insulating material and mounted on or around the frame of the window. The conductor is connected to the non-grounded terminal of the vehicle's electrical battery so as to produce a difference in potential between that conductor and the remainder of the vehicle's body. An electrical capacitor is thus produced such that the entry of a part of the human body into the window opening alters the dielectric of the capacitor. This may be detected by a Wheatstone bridge circuit and stops the movement of the window glass.
An object of the invention, however, is to produce a system with greater sensitivity to the detection of the presence of a part of the human body (or other object), but also with the possibility of being less sensitive to the effects of ambient conditions.
Another system for controlling a power-driven window glass slidable in a window frame is known from German patent specification No. 3,724,085. This system comprises electrically conductive means adapted to be mounted in use adjacent to the window opening so as to be physically moved by direct or indirect contact with part of the human body positioned between the moving window glass and its frame during power-driven closure of the window. This system requires electrical contact to be made between two conductors. Such contact interrupts power-driven movement of the window glass.
Another object of the invention, therefore, is to produce a system which is not affected by ageing and similar effects which may alter the force necessary to achieve the necessary contact in such a system between the conductors.